Rename constants to use *_NONE scheme

Rename constants to use *_NONE scheme

To be uniform across the sources. As a nice side effect
I quickly spotted a couple of needed renames:

captured_piece() -> captured_piece_type()
st->capture      -> st->capturedType

Proposed by Ralph and done with QtCreator

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>